Magnifying point spotting hammer



June 16, 1942. A. M. LAKE MAGNIFYING POINT SPOTTING HAMMER Filed May 8, '1941 INVENTOR flllan/ M Lake BYYS JWu. ATTORNEYS Patented June 16, 1942 UNETED STATES PAl'lEllT OFFICE 2,286,859 MAGNIFYING POINT sro'r'rmc HAMMER Allan M. Lake, Detroit, Mich., assignor to The L. S. Starrett Company, Athol, Mass, a corporation of Massachusetts Application May 8, 1941, Serial No. 392,471

(01. ss+s9 4 Claims.

In punching center points in a fine layout, mechanics with average shop vision have always experienced difficulty in quickly and accurately carrying through the operation including the placing of the point of his punch on the intersection of crossed lines or fine points otherwise marked and ,in then picking up his hammer and striking the punch head with it to get the desired depth of mark at the exact spot on the surface of the metal.

To improve accuracy many workmen used magnifying glasses to assist in getting the punch point on the spot, but this necessitated a steady holding of the point against slipping while, laying down the glass and picking up the hammer. This was so difiicult to do consistently that for fine work many were led to resort to the use of an automatic center punch which was helpful but involved additional expense for the machinists kit. v

My invention contemplates a novel device which makes possible what is a new technique in the art and one which promises to change the old method of performing this operation with any kind of a desired punch. According to my intice of great ease an efilciency. It combines an observational phase and an impact phase in a simple digital manipulative control without the necessity of moving the hand itself from a posed position. Such operation and a simple means for carrying out are illustrated in the accompanying drawing. In the drawing:

Fig. 1 presents a diagrammatic analysis of the components .of the solution of past problems.

Fig. 2 illustrates the hand of a workman grasping the handle of a hammer according to my in vention in the observation phase of its use.

Fig. 3 is a companion View of the hand holding the hammer in striking phase after a digital turn of the handle on the axis of change of phase.

Fig. 4 is a side view of such a hammer as laid on an indicated bench surface.

Fig. 5 is a transverse section of the hammer head taken through the axis of its impact terminals.

Fig. 6 is a longitudinal section through the hammer on a plane intersecting both its impactand its optical axes, and

Fig. '7 is a schematic development of the technique suggested in Fig. 1.

For the practice of my method of center punching, I have devised an improvement in such light hammers whereby: the hammer itself contributes a basic factor in a new technique.

As illustrated, such a hammer may consist of a head I on which are formed a pair of oppositely faced balanced striking terminals 2. The head portion I is preferably formed as a relative ly fiat web and the terminal portions 2 are preferably cylindric in their main cross section behind their striking faces 3. The handle 4 is disposed radially of the head I and is convenient- 1y lightened by the apertures 5, the side walls being slightly rounded as at 4' and connected by a web 6.

The'head I has a central transverse bore 1 in which a slight shoulder I is left by a counterbore 1? the edge of which is formed with a shallow groove into which the split ring 8 is snapped over the edge of the lens 9 marginally to support it in the bore.

Withsuch a hammer held as in Fig. 2, a machinist can observe the spots under any desired magnificaton provided by the lens with which the hammer may be permanently or interchangeably fitted.

The handle 4 may be conveniently held so that its longitudinal axis HH lies across the users fingers, usually supported across the first joint of the forefinger and grasped by the thumb which overlies the broader, flatter side of the handle.

When the point of the center punch indicated as P in the diagrammatic analysis of Fig. 1. has been accurately placed on the spot to be marked, the head I is rotated about its handle axis H--H. This can be effected easily and smoothly by simply sliding the thumb laterally, the second finger assisting. The head can be sorotated either to the right or the left as seems most nat-' ural to the user. When so rotated to bring the axis of the striking terminals into the line B of the intended blow, one or the other of the faces 3 will be in position for striking.

As the handle axis intersects the common axis TT of the balanced terminals midway and also passes through the optical center 0 in the optical axis 0-0 of the lens 9, the hammer assumes the striking phase of this step as illustrated in Fig. 3.

It will be seen therefore that for the old. step of laying down magnifying glass and picking up hammer, my concept substitutes a two-phase step which makes possible a new ease in attaining spotting accuracy.

Hammers according to my invention may be cast or molded with great economy and with a minimum of fitting and finishing. When not in use the oppositely disposed cylindrical striking terminals support the hammer like a pair of trunnions with the lens 9 out of contact with work or bench or other surface on which it may be laid (see Fig 4), and when thus positioned the rear portion of the handle establishes a three-point support for the hammer. The rear portion of the handle is slightly tapered as best shown in Figs. 4 and 6 to establish extended bearing surfaces tangential to the peripheries of said terminals when the hammer is placed either side up on a bench or like supporting surface. This helps to keep the lens surface free from being scratched by metal fragments or particles of abrasive. It also facilitates the proper pick-up of the hammer with the fingers already disposed for convenient and effective posturing on the handle as before described.

My lenses thus marginally supported in the plane of the blow impact therefore would normally, if of glass, be subject to shattering strains across its body and to peripheral chipping at its margin, but I have discovered that I can form a lens from one of the transparent synthetic resinous products available under common trade names, such as Lucite, Plasti-Glas or other socalled trans-plastic materials, which are conveniently thermo-plastic so that I can mold my lenses 9 with suitable bead-like edges which have a certain amount of resilience and resistance to shattering, cracking or chipping when supported in the seat of the head bore.

Lenses of such material which is tough but softer than glass would ordinarily not be available because of their liability to scratch if brought into contact with abrasive, metal filings or other grit necessarily present on the work bench. When mounted as in my hammers, they are protected by the striking terminals of greater diameter than the thickness of the head, as above described.

I have attempted to illustrate the novel technique of the hammer-use. This is difficult within the limits of drawing requirements, but

it will be understood that Fig. 3 is intended. to portray a hammer held in position to deliver a tap on the end of the center punch.

In Fig. '7, it has been attempted to suggest the light finger grasp on the hammer as viewed laterally while being held for observation of the point of a punch P relative to crossed lines L-L as carefully laid out on a small piece of work, such as the block suggested in said figure for 10- cating a desired center spot S.

Various materials and combinations of material may obviously be used in the production of hammers in accordance with my invention and they may be used to advantage in many different types of work where a light hammer and magnification are to be used in a combined operation.

What I therefore claim and desire to secure by Letters Patent is:

1. In a magnifying point spotting hammer, a head including a pair of spaced axially alined oppositely disposed striking terminals, a handle joining said head midway of said terminals with its axis at right angles to the axis of said terminals, said head having an aperture, and a lens supported in said aperture to lie in a plane inclusive of said axes, the peripheries of said terminals andthe end portion of said handle establishing a three-point support for said hammer when the hammer is placed either side up on a plane surface and spacing the lower face of the lens a substantial distance from said plane surface.

2. The hammer of claim 1, the handle having oppositely flattened tapering end portions establishing extended bearing surfaces each occupying a plane tangential to the peripheries of said terminals.

3. A point spotting hammer as in claim 1, in which the magnifying lens is of a shatterproof transparent synthetic material having a hard ness less than that of glass and subject to surface scratching if' brought in contact with the grit of a work bench, v,

4. A hammer, as in claim 1, in which the magnifying lens is of semi-resilient transparent plastic having its edge cushioningly held in the hammer head in the plane of the axis of impact when one of the terminal faces is struck against a resistant tool.

ALLAN M. LAKE. 

